Scientists armed with genetic analysis tools are now coming to a widely-accepted conclusion that the brain and the gut (the unique mix of bacteria, viruses, protozoa, and other bugs inside our gastrointestinal tract) are linked in profound and surprising ways. In fact, your gut may be one of the most important biological systems your body. Scientists pretty much agree that the thousands upon thousands of different strains of bacteria in your intestines are essential to your well-being. Gut bacteria are connected to cancer, autoimmune problems, intestinal bowel disorders, and more. The development of the gut bacteria community in children has been connected to childhood allergies, asthma, and maybe even autism.
The human microbiota is an integral part of our bodies, especially our immune systems. And it is not just gut bacteria, there are bacteria on our skin and in our respiratory tract that are also important for our health. Gut flora, consists of a complex community of bacteria and microorganisms that live in the digestive tracts of humans and animals. In addition to suspected disease related events, theories are being floated that gut microbiomes can influence behavior, mood, fitness and a variety of other functionalities.
It is turning out that the digestive tract, from the esophagus to the stomach and intestines and down to the rectum, functions less like a simple machine and more like a complex ecosystem. Many scientists have even taken to calling the gut and its microbiome “the second brain” and the legion of microbes that live there “the hidden organ.”
There is also communication within the gut itself, and as the microbiota becomes a topic of intense medical interest, so does a mysterious system known as the enteric nervous system (ENS). The ENS lies within the wall of the gut from the esophagus down to the rectum. It has more neurons than the spinal cord and communicates closely with the brain. Moreover, the ENS uses many of the same neurotransmitters that the brain does, like dopamine and serotonin. (In fact, more than 90 percent of the body’s serotonin is located in the gut.) So bacteria in your gut could be hugely important in many of your body’s essential functions. Within just the last few years, some of the scientific breakthroughs reported include findings that:
- Around 20 hormone processes are connected to or have processes in the gut.
- The GI tract contains more than 1 billion nerve endings and has more surface area than that of your external skin. These neurotransmitters, known as the enteric nervous system (ENS) are so involved in your body’s processes, scientists have nicknamed the gut the “second brain.”
- There are over 100 million neurons in the ENS; more than the spinal cord, or the peripheral (outside of the brain or spinal cord) nervous system.
- The brain doesn’t need to operate the GI system. The second brain can act independently. In some cases the ENS sends signals to the brain, not the other way round.
- The “gut-brain axis” describes the influence the gut, microbiome, and ENS have on the brain, including both emotional and cognitive functions.2
- The gut contains 70% to 80% of your body’s immune cells.
But it gets even more remarkable. In 2016 alone, scientists made more startling findings in a number of different areas:
Obesity and metabolic health
Scientists know gut microbiota plays a role in obesity, but previously the research comparing obese and lean individuals had been focused on the ratio of two groups of bacteria: Firmicutes to Bacteroidetes. This year, the research focused in on specific influential species and bacterial metabolites. For instance, researchers recently found that the intestinal bacterium Akkermansia muciniphila improved metabolic health in mice, but also in humans with excess body weight and metabolic syndrome.
The role of gut bacteria in the communication between the enteric nervous system (ENS) – the intestines’ own nervous system – and brain neurons has continued to be a hot topic of study. The ‘gut-brain axis’ is leading to insights beyond the gut. Recent studies have provided more clues about the role of gut bacteria in Parkinson’s disease (PD), showing in mice that gut bacteria from humans with PD worsened motor symptoms. Also in mice, a certain species of gut bacteria was shown to affect social interactions, supporting the idea that probiotics should be further investigated in the treatment of some autism-associated behaviors. Apparently, your gut connects to your brain through the hypothalamus–pituitary–adrenal (HPA) axis, a kind of feedback loop that regulates digestion, stress, immune function, mood, and more. For example, when IBS patients manifest symptoms of anxiety or depression, their doctors may assume that the problem is “all in their head,” but new research suggests that the cause may be signals from their guts—including its microbes—to their brains.
Gut and Sleep Disorders
A study this year examined patients with sleep disorders called CFS. The researchers found that higher levels of the “bad” clostridium bacteria were associated with an increased likelihood of sleep problems and fatigue, but this was specific to females only. This suggests that an unbalanced gut may precipitate or perpetuate sleep problems. Scientists believe that circadian rhythms regulate the gut immune response. The effect of immune cells on the biological clock could provide insights into the possible bidirectional relationship between sleep and the gut. For example, data from animal studies suggests that circadian misalignment can lead to an unbalanced gut microbiota. But this effect can be moderated by diet. There is growing concern that disruptions to our circadian timing of sleep leads to a range of health issues, such as obesity, metabolic and inflammatory disease, and mood disorders. This is particularly important for shiftworkers and others who experience changes to their sleep/wake patterns.
Inflammatory bowel disease (IBD)
Scientists already knew that certain genes were important in predisposing individuals to IBD, but advances this year showed that the way genes could influence IBD-related inflammation is by influencing the gut microbiota. Besides this, it has been confirmed that fungi are as relevant as bacteria in individuals with IBD. And when it comes to predicting the progression towards complicated IBD, new work showed that antibodies produced by the body against microorganisms could lead to insights that could improve diagnosis.
Depression and the Gut
Based on laboratory evidence, the gut microbiota is associated with metabolic disorders such as obesity, diabetes mellitus and neuropsychiatric disorders such as schizophrenia, autistic disorders, anxiety disorders and major depressive disorders. In fact, over the coming years, scientists expect that microorganisms may be developed as a new group of drugs named “psychomicrobiotics” used specifically for the treatment of psychiatric disorders.
Obesity and the Gut
Government researchers indicate overwhelming evidence about important role of gut microbiota in key metabolic diseases, like diabetes and obestity, and their impact upon key pathways like energy homeostasis and inflammation. It’s well known that gut microbiota plays a major role in the development of food absorption and low grade inflammation. Recent studies find that changes in life style that involves increased food consumption and reduced exercise in addition to gut microbiota contribute more to metabolic diseases. As a result, better understanding and utilization of various prebiotic and probiotic bacteria may prove to be beneficial in the treatment of metabolic diseases in the future.
The Dangers of Antibiotics
Unfortunately, these numerous studies have also found that antibiotic usage severely disrupts gut flora health and could contribute to some gut-related disorders, including all of the above discussions. It is now pretty much commonly known that antibiotics cause changes in the intestinal microbiota lead to severe dysregulation in the physiological and immunological intestinal homeostasis, creating serious and adverse consequences for the patient. The problem is that it is difficult to predict exactly what those changes will be and the severity of the damage caused. As a result, doctors are moving away from using antibiotics where they are not absolutely necessary. And researchers are looking into ways in which probiotics are used to supplement antibiotics induced deficits in the microbiota or use immunomodulators to boost a patient’s immune system to combat infections.
Limitations of Probiotics and Dietary Changes
According to John Hopkins researchers, there aren’t foods you can eat specifically to reliably boost your specific gut bacteria, but some contend that a healthy diet low in so-called FODMAPs (starchy, sugary foods) may improve the biodiversity of your gut. Those who suffer from irritable bowel syndrome, for instance, are often advised to avoid FODMAPs. The director of the Johns Hopkins Center for Neurogastroenterology notes that the links between diet and the microbiota are still being studied. But that hasn’t stopped opportunistic marketers from pushing diets and probiotics. The probiotic supplement business is a large and growing industry but, like its vitamin-pushing brethren, it may be pushing useless placebo pills. Sales of probiotic “products” are predicted to exceed $52 billion by 2020. Since 2008, sales for this particular type of supplement has boomed. But are consumers getting anything more than harmless sugar pills for their billions of dollars? The answer is not clear, meaning, as a consumer you need to think carefully before you invest your money into probiotic supplements, foods and other advertised products. The bottom line is that the science simply doesn’t support the slogans pushed by this booming supplement industry. Is it a scam? Possibly! So, we are left with the reality that eating Greek yoghurt for breakfast or popping probiotic pills that contain a couple of Lactobacillus strains is not going to get us very far in terms of building a healthy, flourishing community of hundreds of species of gut microbes. Some high-potency probiotic supplements and probiotic-enriched foods may even do us more harm than good, in the sense that they could stimulate the adult immune system in evolutionarily novel ways and/or block the development of a robust adult gut microbiota. The focus should be on developing a healthy, diverse gut microbiota, not on pouring huge numbers of “probiotics” into the system every day.